<?php

namespace App\Http\Controllers\Api;

use App\Models\InventoryItem;
use App\Models\InventoryMovement;
use App\Models\PurchaseOrderItem;
use App\Models\PurchaseOrder;
use App\Models\Supplier;
use Carbon\Carbon;
use Illuminate\Support\Facades\DB;
use Symfony\Component\HttpFoundation\Response;

class PurchaseOrderController extends BaseApiController
{
    protected PurchaseOrder $po;
    protected PurchaseOrderItem $item;
    protected Supplier $supplier;
    protected InventoryItem $inventoryItem;
    protected InventoryMovement $movement;

    public function __construct()
    {
        parent::__construct();
        $this->po = model(PurchaseOrder::class);
        $this->item = model(PurchaseOrderItem::class);
        $this->supplier = model(Supplier::class);
        $this->inventoryItem = model(InventoryItem::class);
        $this->movement = model(InventoryMovement::class);
    }

    public function index()
    {
        $page   = max(1, (int) ($this->request->getGet('page') ?? 1));
        $perPage= min(100, max(1, (int) ($this->request->getGet('per_page') ?? 20)));
        $keyword= trim((string) ($this->request->getGet('q') ?? ''));

        $query = $this->po->newQuery()
            ->select('purchase_orders.*', 'suppliers.name AS supplier_name')
            ->leftJoin('suppliers', 'suppliers.id', '=', 'purchase_orders.supplier_id')
            ->orderByDesc('purchase_orders.created_at');

        if ($keyword !== '') {
            $query->where(function ($q) use ($keyword) {
                $q->where('po_number', 'LIKE', "%{$keyword}%")
                    ->orWhere('suppliers.name', 'LIKE', "%{$keyword}%");
            });
        }

        $result = $this->paginate($query, $page, $perPage);
        return $this->success($result, 'Purchase orders retrieved successfully');
    }

    public function show($id = null)
    {
        $po = $this->po->newQuery()
            ->select('purchase_orders.*', 'suppliers.name AS supplier_name')
            ->leftJoin('suppliers', 'suppliers.id', '=', 'purchase_orders.supplier_id')
            ->where('purchase_orders.id', $id)
            ->first();

        if (!$po) {
            return $this->error('Purchase order not found', Response::HTTP_NOT_FOUND);
        }

        $items = $this->item->newQuery()
            ->select('purchase_order_items.*', 'inventory_items.name AS supply_name', 'inventory_items.unit AS supply_unit')
            ->leftJoin('inventory_items', 'inventory_items.id', '=', 'purchase_order_items.supply_id')
            ->where('purchase_order_id', $id)
            ->get()
            ->toArray();

        $po['items'] = $items;

        return $this->success($po, 'Purchase order retrieved successfully');
    }

    public function store()
    {
        $user = $this->getCurrentUser();
        if (!$user) {
            return $this->respondError('Authentication required', Response::HTTP_UNAUTHORIZED);
        }

        $payload = $this->payloadData();
        if (empty($payload)) {
            return $this->error('Invalid request data', Response::HTTP_BAD_REQUEST);
        }

        // Support both CodeIgniter-style form arrays and modern JSON format
        $supplyIds = $payload['item_supply_id'] ?? $payload['items'] ?? [];
        $descs = $payload['item_description'] ?? [];
        $qtys = $payload['item_quantity'] ?? [];
        $unitCosts = $payload['item_unit_cost'] ?? [];

        // If items array is provided (modern format), extract data
        if (isset($payload['items']) && is_array($payload['items'])) {
            $items = [];
            foreach ($payload['items'] as $item) {
                if (isset($item['supply_id']) && isset($item['quantity']) && $item['quantity'] > 0) {
                    $items[] = [
                        'supply_id' => $item['supply_id'],
                        'description' => $item['description'] ?? '',
                        'quantity' => (int)$item['quantity'],
                        'unit_cost' => (float)($item['unit_cost'] ?? 0),
                    ];
                }
            }
        } else {
            // CodeIgniter-style form arrays
            if (empty($supplyIds) || !is_array($supplyIds)) {
                return $this->respondError('Add at least one line item.', Response::HTTP_BAD_REQUEST);
            }

            $items = [];
            foreach ($supplyIds as $i => $sid) {
                $q = max(0, (int)($qtys[$i] ?? 0));
                $uc = (float)($unitCosts[$i] ?? 0);
                if ($sid && $q > 0) {
                    $items[] = [
                        'supply_id' => (int)$sid,
                        'description' => trim($descs[$i] ?? ''),
                        'quantity' => $q,
                        'unit_cost' => $uc,
                    ];
                }
            }
        }

        if (empty($items)) {
            return $this->respondError('Valid line items required.', Response::HTTP_BAD_REQUEST);
        }

        $rules = [
            'po_number' => 'required|max_length:255',
            'supplier_id' => 'required|integer',
            'order_date' => 'required|date',
        ];

        $errors = $this->validateRequest($payload, $rules);
        if (!empty($errors)) {
            return $this->respondValidationError($errors);
        }

        try {
            DB::beginTransaction();

            // Compute totals
            $subtotal = 0.0;
            foreach ($items as $item) {
                $subtotal += $item['quantity'] * $item['unit_cost'];
            }

            $tax = (float)($payload['tax'] ?? 0.00);
            $total = $subtotal + $tax;

            $status = $payload['status'] ?? 'ordered';
            $status = in_array($status, ['draft', 'ordered'], true) ? $status : 'ordered';

            $poData = [
                'po_number' => $payload['po_number'],
                'supplier_id' => $payload['supplier_id'],
                'order_date' => $payload['order_date'],
                'expected_date' => $payload['expected_date'] ?? null,
                'status' => $status,
                'subtotal' => $subtotal,
                'tax' => $tax,
                'total' => $total,
                'notes' => $payload['notes'] ?? null,
            ];

            $po = $this->po->create($poData);
            $poId = $po->id ?? null;

            if (!$poId) {
                DB::rollBack();
                return $this->respondError('Failed to create purchase order', Response::HTTP_INTERNAL_SERVER_ERROR);
            }

            foreach ($items as $item) {
                $this->item->create([
                    'purchase_order_id' => $poId,
                    'supply_id' => $item['supply_id'],
                    'description' => $item['description'],
                    'quantity' => $item['quantity'],
                    'unit_cost' => $item['unit_cost'],
                    'received_qty' => 0,
                ]);
            }

            DB::commit();

            $poArray = $this->show($poId)->getData(true)['data'];
            return $this->success($poArray, 'Purchase order created successfully', Response::HTTP_CREATED);
        } catch (\Throwable $e) {
            DB::rollBack();
            log_message('error', 'Purchase order creation error: ' . $e->getMessage());
            return $this->respondError('Failed to create purchase order: ' . $e->getMessage(), Response::HTTP_INTERNAL_SERVER_ERROR);
        }
    }

    public function update($id = null)
    {
        $po = $this->po->find($id);
        if (!$po) {
            return $this->error('Purchase order not found', Response::HTTP_NOT_FOUND);
        }

        $payload = $this->payloadData();
        if (empty($payload)) {
            return $this->error('Invalid request data', Response::HTTP_BAD_REQUEST);
        }

        $allowedFields = ['status', 'expected_date', 'notes'];
        $updateData = [];
        foreach ($allowedFields as $field) {
            if (array_key_exists($field, $payload)) {
                $updateData[$field] = $payload[$field];
            }
        }

        if (empty($updateData)) {
            return $this->error('No valid fields to update', Response::HTTP_BAD_REQUEST);
        }

        try {
            $this->po->update($id, $updateData);
            $updatedPo = $this->po->find($id);
            return $this->success($updatedPo, 'Purchase order updated successfully');
        } catch (\Throwable $e) {
            log_message('error', 'Purchase order update error: ' . $e->getMessage());
            return $this->respondError('Failed to update purchase order', Response::HTTP_INTERNAL_SERVER_ERROR);
        }
    }

    /**
     * POST /api/v1/purchase-orders/{id}/receive
     * Receive items (partial or full) from a purchase order
     */
    public function receive($id = null)
    {
        $po = $this->po->find($id);
        if (!$po) {
            return $this->error('Purchase order not found', Response::HTTP_NOT_FOUND);
        }

        if (in_array($po['status'], ['canceled', 'received'], true)) {
            return $this->respondError('PO not receivable. Status: ' . $po['status'], Response::HTTP_BAD_REQUEST);
        }

        $payload = $this->payloadData();
        $received = $payload['received'] ?? []; // [itemId => qty]

        if (empty($received) || !is_array($received)) {
            return $this->respondError('No items to receive.', Response::HTTP_BAD_REQUEST);
        }

        $user = $this->getCurrentUser();
        $issuedBy = $user ? ($user->email ?? $user->username ?? 'system') : 'system';

        try {
            DB::beginTransaction();

            $completed = true;

            foreach ($received as $itemId => $qty) {
                $qty = (int)$qty;
                if ($qty <= 0) continue;

                $item = $this->item->where('purchase_order_id', $id)->find($itemId);
                if (!$item) {
                    $completed = false;
                    continue;
                }

                $remaining = (int)$item['quantity'] - (int)$item['received_qty'];
                $toReceive = min($remaining, $qty);

                if ($toReceive <= 0) continue;

                // Update item received qty
                $this->item->update($itemId, [
                    'received_qty' => (int)$item['received_qty'] + $toReceive
                ]);

                // Update inventory item on hand (if supply_id maps to inventory_items)
                if (!empty($item['supply_id'])) {
                    $inventoryItem = $this->inventoryItem->find($item['supply_id']);
                    if ($inventoryItem) {
                        $newQty = (int)($inventoryItem['quantity'] ?? 0) + $toReceive;
                        $this->inventoryItem->update($inventoryItem['id'], [
                            'quantity' => $newQty
                        ]);

                        // Log transaction IN using inventory movements
                        $this->movement->insert([
                            'item_id' => $inventoryItem['id'],
                            'qty_change' => $toReceive,
                            'movement_type' => 'in',
                            'reason' => 'PO ' . $po['po_number'],
                            'note' => 'Received against PO',
                            'performed_by' => $this->getCurrentUserId() ?? null,
                        ]);
                    }
                }

                if (($item['received_qty'] + $toReceive) < $item['quantity']) {
                    $completed = false;
                }
            }

            // Set PO status
            $this->po->update($id, [
                'status' => $completed ? 'received' : 'ordered'
            ]);

            DB::commit();

            $message = $completed ? 'PO fully received.' : 'PO partially received.';
            return $this->success(null, $message);
        } catch (\Throwable $e) {
            DB::rollBack();
            log_message('error', 'Receive PO error: ' . $e->getMessage());
            return $this->respondError('Failed to receive items: ' . $e->getMessage(), Response::HTTP_INTERNAL_SERVER_ERROR);
        }
    }

    /**
     * POST /api/v1/purchase-orders/{id}/cancel
     * Cancel a purchase order
     */
    public function cancel($id = null)
    {
        $po = $this->po->find($id);
        if (!$po) {
            return $this->error('Purchase order not found', Response::HTTP_NOT_FOUND);
        }

        if ($po['status'] === 'received') {
            return $this->respondError('Cannot cancel a received PO.', Response::HTTP_BAD_REQUEST);
        }

        try {
            $this->po->update($id, ['status' => 'canceled']);
            $updatedPo = $this->po->find($id);
            return $this->success($updatedPo, 'PO canceled.');
        } catch (\Throwable $e) {
            log_message('error', 'Cancel PO error: ' . $e->getMessage());
            return $this->respondError('Failed to cancel purchase order: ' . $e->getMessage(), Response::HTTP_INTERNAL_SERVER_ERROR);
        }
    }
}